High voltage power distribution systems play an important role in modern society. Safety and security are always considerable factors for the “health” of such high voltage power distribution system. Accordingly, there should be a technology that enables monitoring of the “health” of the high voltage power distribution system.
In a high voltage power distribution system, the temperature of conductors of electrical cables will increase as currents carried by the cables increase. Accordingly, the “health” of such system can be assessed by monitoring the temperature of the on-line electrical conductor, for example, at the cable splices or the junctions, which may be the weak points, in such a system. Usually, normal currents flowing through the cable splices or the junctions may create a temperature of up to about 90 degrees Celsius. If the temperatures of the cable splices or the junctions were to increase beyond that, it could be an indication that something may be wrong in this power distribution system. On the other hand, it is also useful to know if the existing power distribution system is at maximum current carrying capacity, to know if additional power can be reliably distributed with the existing system, or, to know if additional infrastructure expenditures are needed.
On-line power cables, as well as the cable splices and the junctions, in high voltage power distribution systems are typically insulated and protected by a number of insulative and (semi)conductive layers and are commonly buried underground or are high overhead. Therefore, it is not easy to monitor the temperature of the on-line electrical conductor, for example, directly at the cable splices or the junctions.
As used in this specification:
“(semi)conductive” indicates that the layer may be semi-conductive or conductive, depending on the particular construction.
“thermal contact” between two articles means that the articles can exchange energy with each other in the form of heat.
“direct contact” between two articles means physical contact.
FIG. 1 illustrates a type of standard high voltage cable splice assembly 30 in which two sections of an electrical cable 10 are spliced. As shown in FIG. 1, the electrical cable 10 comprises electrical conductor 31, insulation layer 33, and (semi)conductive layer 35. A connector 12 concentrically surrounds the spliced electrical conductor 31. A first (semi)conductive (or electrode) layer 13, in this case a metallic layer, concentrically surrounds the spliced electrical conductor 31 and the connector 12, forming a shielding Faraday cage around the connector 12 and electrical conductor 31. An insulating layer 11 (containing geometric stress control elements 16) surrounds the first (semi)conductive layer 13. The foregoing construction is placed inside a second (semi)conductive layer 14, in this case a metallic housing, which functions as a shield and ground layer. A resin 17 is poured into the metallic housing 14 through one of the ports 18 to fill in the area around insulating layer 11. And a shrinkable sleeve layer 15 serves as an outermost layer.
Therefore there is a need to develop a solution to monitor the temperature of an electrical conductor enclosed in at least a (semi)conductive layer, for example, in a high voltage power distribution system.